I'm receiving conflicting information on which ball joints to use. A Arms are modded, stock cavy knuckle... Which ball joints? Alero or Cavy? My Cavy ones are fairly knew <6k don't want to buy new if I don't have to.

Not only just your view, its the only way it will correctly work. ALWAYS match the balljoint to the knuckle you are using. I think i posted this before but the mesasurements are different, as well as the taper.

The gold colored joint is for aluminum spindles/arms. The gray is j-body. :

Notice how the J-body joint has a slight taper and then straightens out, whereas the N-body joint is a bigger, continuous taper.

The N-body joint is also physically longer.

The N-body joint is a tiny bit smaller at the beginning of the taper compared to the J-body joint.

The J-body joint straightens out and is significantly smaller than the N-body joint at the end of the taper.